Method of and apparatus for disinfecting liquids by anodic oxidation with a silver anode

ABSTRACT

This invention is directed to the disinfection of liquids, especially water-containing liquids. It has been found that by the simultaneous use of anodic oxidation and silver ions a synergistic disinfection effect is achieved.

United States Patent Eibl et al.

Dec. 2, 1975 METHOD OF AND APPARATUS FOR DISINFECTING LIQUIDS BY ANODIC OXIDATION WITH A SILVER ANODE Inventors: Volker Eibl; August Reis. both of Munich, Germany Sachs-Systemtechnik GmbH, Schweinfurt am Main, Germany Filed: May 28, 1974 Appl. No.: 473,389

Assignee:

Foreign Application Priority Data June 9, 1973 Germany 2329628 US. Cl. 204/301; 204/149; 204/151 Int. Cl. C02B 1/82 Field of Search 204/149, 151, 130, 301

Primary Exa'miner-John H. Mack Assistant Examt'nerA. C. Prescott Attorney, Agent, or FirmHans Berman; Kurt Kelman [57] ABSTRACT This invention is directed to the disinfection of liquids, especially water-containing liquids. It has been found that by the simultaneous use of anodic oxidation and silver ions a synergistic disinfection effect is achieved.

2 Claims, 1 Drawing Figure METHOD OF AND APPARATUS FOR DISINFECTING LIQUIDS BY ANODIC OXIDATION WITH A SILVER ANODE The object of this invention is to disinfect water, polluted water and beverages provided for human or animal use.

The invention provides a method for disinfecting liquids. especially water-containing,liquids, in which the liquid to be disinfected is subjectedto the effect of an electric current in an electrolytic cellcomprising an anode and a cathode, the anode being made of silver or a silver-containing. material, the. disinfection, taking place substantially in the electrolytic. cell.

By this invention disinfective additives are avoided. To avoid such additives is an improvement because it is difficult to add said additives in the just amount and frequently the liquid is inadmissibly influenced by the additives. By this invention is is not only possible to disinfect, it is also possible to decontaminate and to detoxicate such liquids, or the contaminations and poisons resp. can be converted into non-toxic compounds.

The amount of silver ions entering into the liquid can be smaller than the amount which is necessary, if one merely relies on silver ions for the disinfection. So if is possible to work with very small amounts of silver.

For the man skilled in the art who is provided with the above knowledge and with the following details it is easy to chose the anode surface, the form and the size of the flow passage and the flow rate such that the present disinfection is substantially completed during the passage through the electrolytic cell.

It has been found that a good disinfection is obtained if the following relationship is true:

F, g k V wherein F, is the anode surface in cm and V is the flow rate in cm per sec and k is a constant having the value 5/3 sec/cm and implying the distance between the anode and the diaphragm and the reaction time.

This relationship has been found by experiments. It has further been found that the constant k should not be greater than 6 sec/cm in order to maintain the size of the apparatus at the necessary minimum and in order to avoid too long periods of treatment which could result in the generation of undesired compounds in an inadmissible concentration.

If contaminations or poisons are present in the liquid to be treated, the relationship between the electrode surface and the electrolytic cell must be such that the contaminations and poisons resp. are reduced to a desired value within the cell. It is frequently necessary to adapt the surface of the electrode to the specific contaminations and/or poisons. This relationship can be found by someone skilled in the art by simple experiments, when considering that a certain minimum of concentration of the contaminations or poisons must be achieved on the one hand and the investment for the apparatus should be kept at a minimum at the other hand.

The invention will now be further described by reference to the enclosed drawing.

Other features and many of the attendant advantages of this invention will readily be appreciated as the same becomes better understood by reference to the following detailed description of a preferred embodiment when considered in connection with the appended drawing.

In the drawing the reference number 1 denotes the container of the electrolytic cell, 2 is the anode and 4 the-cathode. The current supply to the electrodes oc-. curs via leads 3 (anode) and 5 (cathode). 6 denotes the.

cathode compartment of the cell, 7 the anode compartment und 8 the diaphragm dividing the space in container 1 into said two compartments. 9 denotes the water inlet and 10 the outlet for withdrawing purified water.

The method of operation of the apparatus is as follows: i

The liquid to be disinfected in the case of the embodiment drinking water-Jflows-through the water inlet 9 into the anode compartment] and is subjected there to an oxidation process due to the current flow between the anode plate 2 and-the cathode plate 4. Thereby electrons are abstracted and oxygen is added. The oxidizing effect, i.e. the abstraction of electrons, is very effective, for also normally badly oxydizing substances are affected. This is also true for the microorganisms within the water which, since being organic compounds, are decomposed by oxidation and, accordingly, are destroyed. As diaphragm 8 an asbestos sheet can be used, but particularly advantageous results have been obtained with a material only permeable to anions, since in this case a concentration of anions in the anode compartment 7 takes place. The cathode compartment 6 is suitable provided with a deaerationor passage possibility so as to be able to evacuate hydrogen occurring in very small quantities.

For the tests carried out voltages between the electrodes in the magnitude of 8 l0 volts are used. It is important that current intensities are used which ly below the current intensities necessary for the electrolysis of the water, so that no large scale liquid decomposition and degasing of hydrogen and oxygen occurs. The current intensities used for the tests in this context are in the magnitude of mA, whereby a good oxydizing effect was obtained. A sufficient oxydizing effect also exists if the diaphragm 8 is omitted. In this case no separate cathode compartment 6 exists so that it is not necessary to provide any particular structural measure for dearation of or passage through said compartment.

The tests carried out with the silver anode obtained an increased effectiveness with respect to germ extinction both over an anodic oxidation per se as a degermination agent and over the degermination effect of electrolytically precipitated silver. At equal apparatus dimensions and starting from germ numbers 10 to 10 coli germs per ml, both at anodic oxidation without a silver anode and at a treatment with electrolytically precipitated silver a reduction of the number of germs to about 10 to 10" coli per ml after a reaction period of 2 to 3 minutes in the test device resulted, a concentration which even upon extension of the reaction period remained substantially constant and, at the most, slightly increased. Upon comparison tests with silver anodes in the same apparatus with corresponding numbers of germs, no germs could be ascertained after a circulation time of 40 sec at the latest. Particularly good results were obtained upon use of a diaphragm permeable to anions, whereby after a circulation time of 20 sec no germs existed any longer.

This increased effectiveness of the inventive method and of the apparatus does not reside in an addition effect of the two known methods of disinfection by anodic oxidation or electrolytic silver precipitation. As explained above, the effectiveness goes far beyond a combination of both processes, whereby the essence compartment, said conductive material consisting at least partly of metallic silver;

d. a cathode in said cathode compartment;

e. leads connected to said anode and to said cathode respectively for passing electric current through said liquid in said space between said cathode and said anode;

f. inlet means for admitting said contaminated water to said anode compartment; and

g. outlet means for withdrawing purified water from said space.

2. Apparatus as set forth in claim 1, wherein said anode compartment essentially consists of silver. 

1. APPARATUS FOR PURIFYING WATER CONTAMINATED WITH MICROORGANIMS WHICH COMPRISES: A. A CONTAINER ENCLOSING A SPACE ADAPTED TO HOLD SAID WATER, B. A DIAPHRAGM DIVIDING SAID SPACE INTO AN ANODE COMPARTMENT AND A CATHODE COMPARTMENT, SAID DIAPHRAGM BEING PERMEABLE TO ANIONS ONLY; C. AN ANODE OF CONDUCTIVE MATERIAL IN SAID ANODE COMPARTMENT, SAID CONDUCTIVE MATERIAL CONSISTING AT LEAST PARTLY OF METALLIC SILVER; D. A CATHODE IN SAID CATHODE COMPARTMENT; E. LEADS CONNECTED TO SAID ANODE AND TO SAID CATHODE RESPECTIVELY FOR PASSING ELECTRIC CURRENT THROUGH SAID LIQUID IN SAID SPACE BETWEEN SAID CATHODE AND SAID ANODE; F. INLET MEANS FOR ADMITTING SAID CONTAMINATED WATER TO SAID ANODE COMPARTMENT; AND G. OUTLET MEANS FOR WITHDRAWING PURIFIED WATER FROM SAID SPACE.
 2. Apparatus as set forth in claim 1, wherein said anode compartment essentially consists of silver. 